/usr/share/octave/packages/general-1.3.4/unresamp2.m is in octave-general 1.3.4-2.
This file is owned by root:root, with mode 0o644.
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##
## This program is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free Software
## Foundation; either version 3 of the License, or (at your option) any later
## version.
##
## This program is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
## details.
##
## You should have received a copy of the GNU General Public License along with
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn{Function File} {[@var{xs}, @var{ys}] =} unresamp2 (@var{x}, @var{y}, @var{n})
## Perform a uniform resampling of a planar curve.
## The arrays @var{x} and @var{y} specify x and y coordinates of the points of the curve.
## On return, the same curve is approximated by @var{xs}, @var{ys} that have length @var{n}
## and the distances between successive points are approximately equal.
## @end deftypefn
## Author: Jaroslav Hajek <highegg@gmail.com>
function [xs, ys] = unresamp2 (x, y, n)
if (! isvector (x) || ! size_equal (x, y) || ! isscalar (n))
print_usage ();
endif
if (rows (x) == 1)
rowvec = true;
x = x.'; y = y.';
else
rowvec = false;
endif
# first differences
dx = diff (x); dy = diff (y);
# arc lengths
ds = hypot (dx, dy);
# cumulative integral
s = cumsum ([0; ds]);
# generate sample points
i = linspace (0, s(end), n);
if (! rowvec)
i = i.';
endif
# and resample
xs = interp1 (s, x, i);
ys = interp1 (s, y, i);
endfunction
%!demo
%! R = 2; r = 3; d = 1.5;
%! th = linspace (0, 2*pi, 1000);
%! x = (R-r) * cos (th) + d*sin ((R-r)/r * th);
%! y = (R-r) * sin (th) + d*cos ((R-r)/r * th);
%! x += 0.3*exp (-(th-0.8*pi).^2);
%! y += 0.4*exp (-(th-0.9*pi).^2);
%!
%! [xs, ys] = unresamp2 (x, y, 40);
%! plot (x, y, "-", xs, ys, "*");
%! title ("uniform resampling")
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